package com.hmdp.utils;

import cn.hutool.core.lang.UUID;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;

import java.util.Collections;
import java.util.concurrent.TimeUnit;

public class SimpleRedisLock implements ILock {

    private String name;
    private StringRedisTemplate stringRedisTemplate;
    public SimpleRedisLock(String name, StringRedisTemplate stringRedisTemplate) {
        this.name=name;
        this.stringRedisTemplate = stringRedisTemplate;
    }

    private static final String KEY_PREFIX = "lock:";
    private static final String ID_PREFIX = UUID.randomUUID().toString(true) + "-";
    private static final DefaultRedisScript<Long> UNLOCK_SCRIPT;
//    静态代码块：可以使得首次加载便能初始化完成脚本，而无需多次的io调用
    static {
        UNLOCK_SCRIPT = new DefaultRedisScript<>();
        UNLOCK_SCRIPT.setLocation(new ClassPathResource("unlock.lua"));
        UNLOCK_SCRIPT.setResultType(Long.class);
    }
    @Override
    public boolean tryLock(long timeoutSec) {
//      获取线程标示
        String threadId = ID_PREFIX + Thread.currentThread().getId();
//      获取锁
        Boolean success = stringRedisTemplate.opsForValue()
                .setIfAbsent(KEY_PREFIX + name, threadId , timeoutSec, TimeUnit.SECONDS);
        return Boolean.TRUE.equals(success);
    }

    @Override
    public void unlock() {
        stringRedisTemplate.execute(
                UNLOCK_SCRIPT,
                Collections.singletonList(KEY_PREFIX + name),
                ID_PREFIX + Thread.currentThread().getId()
        );
    }

/*
    //存在原子性问题
    @Override
    public void unlock() {
//      获取当前线程的标示
        String threadId  = ID_PREFIX + Thread.currentThread().getId();
//        获取锁（redis）中的标示
        String idCache = stringRedisTemplate.opsForValue().get(KEY_PREFIX + name);
//        判断是否一致
        if(threadId.equals(idCache)){
//            释放锁
            stringRedisTemplate.delete(KEY_PREFIX + name);
        }
    }
*/

}
